Circuit card assemblies (CCA's) or printed circuit boards (PCB's) are often mounted onto a housing or support structure (it is noted that while the term CCA may be used to refer to a PCB that has had electronic components physically attached and electrically connected thereto, the terms are often used interchangeably and may be used interchangeably with respect to the disclosure herein). This may be done for a variety of reasons, including providing a heat sink to manage heat generated during operation of the CCA and/or to provide a secure location proximate to system components with which the electronic circuitry of the CCA interact during operation.
One method of mounting a CCA to a housing is to pot the CCA in a resin that is retained by the housing. However, potting the CCA in a housing is in many cases not a viable solution due to a number of issues such as inability to readily remove the CCA from the housing for repair or replacement thus necessitating replacement of the entire mounted assembly, extended times required to cure the resin mass in which the CCA is potted (which is often not acceptable for high-volume rapid manufacturing such as in the motor vehicle field), dimensional stability issues associated with curing the resin mass (e.g., shrinkage, cracking, etc.), poor thermal conductivity of the resin mass, which can interfere with the ability of the CCA to transfer heat to a heat sink for thermal management purposes, and difficulties associated with providing an electrical path to ground through the resin mass.
Accordingly, mounting hardware such as screws have often been used to mount CCA's or PCB's to housings. Mounting screws offer certain advantages, such as ease of removal of the CCA from the housing for repair or replacement. The use of mounting screws, however, causes a number of problems as well. One issue with the use of mounting screws to secure a CCA to a housing is that they cause bending in the CCA, which in turn creates strain. In order to properly secure a CCA to a housing, multiple mounting screws are usually required. If the mounted CCA is to be used in an environment subject to vibration, it may be necessary to tune the modal response of the CCA at least one octave above the resonant frequency of the environmental vibration in order to provide avoid premature vibration-induced failure of the CCA, which can require even more mounting screws. Such use of multiple mounting screws further exacerbates the bending and resultant strain on the CCA. The screw-induced strain on the CCA is greatest in the areas adjacent to each screw, which can lead to premature failure of electronic components or soldered electrical connections in those areas. Attempts to avoid such electrical connection failure have included adding additional layers to the structure of the PCB to mitigate strain, which increases cost. Another technique to manage the strain caused by mounting screws is to design the CCA with ‘keep-out’ zones around the screw mounting positions. Electrical components and connection pathways are kept out of these keep-out zones, resulting in an increase in the footprint size of the CCA, which both increases cost and often places undesirable design constraints on the system into which the CCA will be incorporated.
Accordingly, it would be desirable to provide a mounted CCA or PCB that would not be subject to the above-described problems.